1. Field of the Invention
The present invention relates to a three-dimensional discharge electrode that effectively and stably discharges, and to a photocatalysis apparatus employing the three-dimensional discharge electrode and a photocatalyst that becomes active when irradiated with light (ultraviolet rays) emitted from the electrode and removes hazardous substances.
2. Description of the Related Art
It is well known that hazardous substances such as dioxins and NOx contained in the atmosphere or water cause environmental pollutions. To effectively remove the hazardous substances, various studies have energetically been made. There are hazardous substances that cause problems in closed spaces, such as putrid gas like ethylene gas in refrigerators, sick-house-syndrome causing chemicals like formaldehyde, toluene, xylene, and aradichlorobenzene in houses, and tobacco fumes in rooms or cabins.
To remove such hazardous substances, discharge apparatuses using electric discharge and photocatalysis apparatuses using photocatalysts have been developed.
FIG. 1 shows a photocatalysis apparatus 101 according to a related art.
The photocatalysis apparatus 101 has a casing 102, a photocatalyst 103 carrying titanium oxide (TiO2) and housed in the casing 102, a pair of thin-film electrodes 104 arranged on each side of the photocatalyst 103, and a high-voltage power source 105 to apply a high voltage to the electrodes 104. Receiving the high voltage, the electrodes 104 discharge. The discharge produces light (ultraviolet rays) to activate the titanium oxide of the photocatalyst 103. The activated photocatalyst 103 removes hazardous substances from incoming gas. When activated with ultraviolet rays, the photocatalyst 103 produces hydroxy radicals (.OH) and super-oxide anions (.O2—). The hydroxy radicals are strongly oxidative to dissociate the molecular. The apparatus 101 uses the oxidizing power of the hydroxy radicals, to chemically remove hazardous substances.
This related art has some problems. The electrodes 104 are made of thin films and are vulnerable to corrosive substances such as hydrogen sulfide, sulfurous acid, nitrous acid, chlorine, and ammonia among hazardous substances to remove.
Once the electrodes 104 corrode due to such corrosive substances, the corroded part carries out no discharge, and therefore, the electrodes 104 unevenly discharge. If the corrosion develops further, the electrodes 104 will become partly nonconductive to worsen the uneven discharge. Then, the photocatalyst 103 will unevenly be activated to provide insufficient catalytic performance.
The thin-film electrodes 104 are unstable when installed. The electrodes 104 must be kept in parallel with each other to maintain the effect and efficiency of the photocatalyst 103. The electrodes 104 made of thin films easily shift, deform, or break if installed improperly or if exposed to excessive conditions such as a high flow rate of hazardous substances or a large amount of dust. If such trouble occurs, the electrodes 104 will emit insufficient ultraviolet rays for the photocatalyst 103.